Feline Vaccines and Adjuvant: Good Intentions and the Road to ….

“Adjuvant” is a substance added to a drug to increase or enhance its effect. Many vaccines incorporate an adjuvant in order to help the vaccine provide stronger, more effective protection against disease – sounds like a good idea, doesn’t it? And for most mammals, including dogs, it is. However, as we were taught so often in veterinary school, cats are not small dogs. Indeed, sometimes it seems that no two mammals could be more different!

Adjuvant may well provoke a stronger immune reaction to the vaccine, but in cats it also provokes a reaction from the connective tissue surrounding the vaccination site. In a very small percentage of cats, that reaction will eventually turn into a cancer of connective tissue called fibrosarcoma. Vaccine-induced sarcoma is one of the more tragic dilemmas of veterinary medicine: in trying to help our patients, we may inadvertently do harm.

The risk of diseases such as rabies, feline leukemia and feline distemper far outweighed the risk of the vaccine, so there has never been any question about whether to vaccinate – for these diseases, at least, we simply must. Nonetheless, the doctors at KAMC have tried to minimize the risk of vaccine-induced sarcoma in a variety of ways. We vaccinate only for the diseases listed above, use vaccines without adjuvant whenever possible, and give those vaccines as infrequently as possible.

We have used non-adjuvanted vaccines for rabies and feline distemper (aka FVRCP) for years. Now, thankfully, we have a non-adjuvanted leukemia vaccine as well. Of course, many of our feline patients will never receive the vaccine. We only administer a leukemia vaccine to at-risk patients: namely, cats who go outdoors or who live with another cat that has leukemia.

Our new feline leukemia vaccine is not delivered through a syringe. A “gun” is instead used to deliver the vaccine with a burst of air. The device looks like something out of an old Star Trek episode, but it works well. Cats rarely even flinch when the new vaccine is given. The air burst is specifically calibrated for feline skin, although it can certainly sting if a human decides to test it on himself . . . don’t ask us how we know!

Dr. Charles H. Livaudais